Phillip Susi wrote:
Right, the kernel does not know how many disks are in the array, so it
can't automatically increase the readahead. I'd say increasing the
readahead manually should solve your throughput issues.
Any guesses for a good number?
We're in RAID10 (2+2) at the moment on 2.6.8-smp. These are the block
numbers I'm getting using bonnie++ :
ra wr rd
256 68K 46K
512 67K 59K
640 67K 64K
1024 66K 73K
2048 67K 88K
3072 67K 91K
8192 71K 96K
9216 67K 92K
16384 67K 90K
I think we might end up going for 8192.
We're still wondering why rd performance is so low - seems to be the
same as a single drive. RAID10 should be the same performance as RAID0
over two drives, shouldn't it?
Max.
Max Waterman wrote:
I left the stripe size at the default, which, I believe, is 64K bytes;
same as your fakeraid below.
I did play with 'blockdev --setra' too.
I noticed it was 256 with a single disk, and, with s/w raid, it
increased by 256 for each extra disk in the array. IE for the raid 0
array with 4 drives, it was 1024.
With h/w raid, however, it did not increase when I added disks. Should
I use 'blockdev --setra 320' (ie 64 x 5 = 320, since we're now running
RAID5 on 5 drives)?
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